System for post-processing polymeric items

ABSTRACT

A system and method for post-processing of polymeric items having a liquid component and a predetermined heat deflection temperature is provided. The system includes a washing station to spray water at elevated temperature and pressure on the items while maintaining the temperature of the item below the heat deflection temperature. Then using a water distillation system to separate the water from the water mixed with the liquid polymer component by evaporating the water using heating coils with surface that is not conducive to adhesion of the liquid polymer component and then condense the water vapor into liquid water. The system may further include a spin station to separate the liquid polymer component by spinning the item. The system may further include one or more processing stations to rinse the item, dry the item, cure the item, remove the item from a tray to which the item may be attached and clean trays after removing the item. A conveyor system may be used to automate the post-processing of the items.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of co-pending U.S. patentapplication Ser. No. 15/949,946, filed on Apr. 10, 2018, now U.S. Pat.No. 10,779,915; which is a continuation of U.S. patent application Ser.No. 14/297,393, filed on Jun. 5, 2014, now U.S. Pat. No. 10,004,578;which is a divisional of U.S. patent application Ser. No. 11/781,809,filed on Jul. 23, 2007, now U.S. Pat. No. 8,776,391; which is acontinuation of U.S. patent application Ser. No. 11/735,367, filed Apr.13, 2007, now abandoned. The disclosures of all of the foregoingapplications are hereby incorporated herein by reference in theirentireties.

FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to the field of fabricating molds polymericitems, and more specifically, to an automated system for thepost-processing of polymeric molds, particularly molds for fabricatingplastic orthodontic appliances.

2. Background

Stereolithography is a rapid prototyping process used to create solid,plastic, three-dimensional (3-D) objects, such as molds, from CADdrawings. For example, stereolithography is used to fabricate molds thatare used to make plastic orthodontic alignment appliances, as described,for example, in U.S. Pat. No. 5,975,893 and US Patent ApplicationPublication 2005/0082703, both of which are commonly assigned to theassignee of the subject invention, and the disclosures of which are bothincorporated herein by reference.

Plastic orthodontic appliances, of the type disclosed in theabove-referenced documents, are made as a set of incremental positionadjustment appliances that are used to realign or reposition a patient'steeth. The series of incremental position adjustment appliances iscustom made for each patient during the fabrication process.

The fabrication process starts with a dentist making impressions orcasts of the upper and lower dental arches of a patient. The impressionsor casts are then sent by the dentist to an orthodontic appliancemanufacturing facility. The manufacturing facility creates a treatmentfile from the impressions or casts that includes the treatmentinformation for the patient. Treatment information includes the numberof stages (i.e. each appliance in the series of incremental positionadjustment appliances represents a stage) for both the upper and lowerdental arches that are required for repositioning the patient's teeth,as well as how the patient's teeth move during each stage. The treatmentfile is then sent to the dentist for approval. Upon approval, themanufacturing facility generates 3D CAD models or images of molds formaking the appliances using the treatment file, and then creates themolds using a rapid prototyping process, such as, for example,stereolithography. The molds are then used to fabricate the appliances.

Once the molds have been created, the molds are subjected to severalpost-processing steps. Currently, the post-processing of the molds isdone manually, and includes removing any debris and any excess moldmaterial (i.e., polymeric resin) from the molds. To clean the molds,they are first soaked in a solvent, and then they are sprayed with waterand air to remove the excess resin and the loosened debris, and to rinseoff the solvent.

The solvent used to clean the molds is toxic to the environment, andusing fresh water to rinse off the solvent results in a significantconsumption of water. Additionally, manually cleaning the molds islabor-intensive, and therefore entails substantial costs and time toproduce the items. Accordingly, there is a need for an efficient systemand method to improve productivity by automating the post-processing ofthe molds, using only water to clean the molds, and purifying the usedwater and waste resin from the molds to be reused.

SUMMARY OF THE INVENTION

As used herein, the terms “the invention” and “the present invention”shall encompass the specific embodiments disclosed herein, as well asany and all equivalents that may suggest themselves to those skilled inthe pertinent arts.

In one aspect, the present invention is a system for removal ofextraneous liquid material dispersed on an item, the system comprising amotor-driven platform having an axis of rotation and configured toremovably hold the item radially displaced from the axis of rotation,wherein the platform is operable to rotate the item about the axis so asto separate the liquid from the item by centrifugal force while the itemis held by the platform. In an exemplary embodiment of the invention,the items are polymeric molds for manufacturing plastic orthodonticappliances.

In a second aspect, the present invention is a system forpost-processing of polymeric items having a liquid polymer component anda predetermined heat deflection temperature, the system comprising: awashing station operable to remove the liquid polymer component from theitems, the washing station including a water spraying mechanism operableto spray water at elevated temperature and pressure on the items whilemaintaining the temperature of the items below the heat deflectiontemperature of the items and a water distillation system arranged toreceive the portion of the mixture of water and the liquid polymerremoved from the item by the washing station, and operable to separateby distillation the water from the liquid polymer in the mixture;wherein the distillation system comprises: a reaction chamber operableto maintain vacuum and having a heating coil operable to separate theliquid polymer and water by evaporating the water, wherein the heatingcoil has a surface that is not conducive to adhesion of the liquidpolymer during the separation; and a condensation chamber arranged toreceive water vapor from the reaction chamber and operable to condensethe water vapor into liquid water. In an exemplary embodiment of theinvention, the items are polymeric molds for manufacturing plasticorthodontic appliances.

In a third aspect, the present invention is a method for post-processingof polymeric items having a liquid polymer component and a predeterminedheat deflection temperature, wherein the method comprises: sprayingwater at elevated temperature and pressure on the items whilemaintaining the temperature of the items below the heat deflectiontemperature of the items and removing liquid polymer from the items;receiving a mixture of water and the liquid polymer removed from theitems and separating a portion of the mixture of water and the liquidpolymer; separating the water from the liquid polymer in the mixture bydistilling the mixture of water and the liquid polymer by subjecting themixture of water and the liquid polymer to heat using heating coils notconducive to adhesion of the liquid during separation and under vacuum,and evaporating the water; and condensing the water vapor into liquidwater.

In a fourth aspect, the present invention is a system forpost-processing of polymeric items having a liquid polymer component,the system comprising: a motor-driven turntable having an axis ofrotation and configured to removably hold the item radially displacedfrom the axis of rotation, wherein the turntable is operable to rotatethe item about the axis so as to separate the liquid from the item bycentrifugal force while the item is held by the turntable; a washingstation operable to spray water at elevated temperature and pressure onthe items to remove the liquid polymer component from the item; and awater distillation system arranged to receive a portion of the mixtureof water and the liquid polymer removed from the item by the washingstation and operable to separate by distillation the water from themixture of water and the liquid polymer. In a fifth aspect, the presentinvention is a for post-processing of polymeric items, the systemcomprising: a tray, the item attached to the tray by a sacrificial layerof the polymer; a detachment station operable to apply sufficientpressure to the item to separate the item from the tray by breaking thesacrificial layer; and a transfer plate including a plurality of movablepins, the transfer plate operable to position the movable pins to engagewith the item and move the item relative to the tray. This brief summaryhas been provided so that the nature of the invention may be understoodquickly. A more complete understanding of the invention can be obtainedby reference to the following detailed description of the preferredembodiments thereof in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features and other features of the present invention willnow be described with reference to the drawings of a preferredembodiment. In the drawings, the same components have the same referencenumerals. The illustrated embodiment is intended to illustrate, but notto limit the invention. The drawings include the following Figures:

FIG. 1 is a block diagram of a system for processing polymeric resinitems, such as polymeric molds, according to one aspect of the presentinvention;

FIG. 2 is a perspective view of an exemplary spin station for use in thesystem of FIG. 1;

FIG. 3A is a perspective view of an exemplary spin chamber for use inthe exemplary spin station of FIG. 2;

FIGS. 3B and 3C are detailed perspective views of an exemplary clampassembly for use with the exemplary spin chamber of FIG. 3A;

FIG. 4 is a block diagram of an exemplary embodiment of a washingapparatus for use in the system of FIG. 1;

FIGS. 5A and 5B comprise a flow schematic of an exemplary washingapparatus for use in conjunction with the washing apparatus of FIG. 4;

FIG. 6 is a block diagram of an exemplary distillation system for use inthe water filtration system shown in FIG. 5B; and

FIG. 7 is a closed loop water flow chart for use with the washingapparatus of FIG. 4.

FIG. 8 is an air handling system for use with the washing apparatus ofFIG. 4.

FIG. 9 is a perspective view of an exemplary removal station for use inthe system of FIG. 1;

FIG. 9A is a detailed perspective view of a transfer plate for use withthe exemplary removal station of FIG. 9.

FIG. 10 is a side view of an exemplary cleaning station for use in thesystem of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a system and method for the processing,or “post-processing,” of uncured polymeric resin items, such as, forexample, dental appliance molds created by a rapid prototypingapparatus, such as a stereolithography apparatus (SLA). Post-processingincludes one or more steps of removing any liquid or semi-liquid resinin or on the items after they are created, removing any debris andexcess resin from the items, curing the items to increase theirstrength, removing the items and any excess support material from a trayor platform on which the items are held, and recovering any excess resinfor reuse or disposal. The invention is described herein in the contextof polymeric resin molds fabricated in an SLA. More specifically, themolds may be those used in the fabrication of plastic orthodonticappliances. Although the specific implementation of the fabrication ofmolds for plastic orthodontic appliances is described herein, thepresent invention can be utilized with any items created by SLA or otherapparatus (especially rapid prototyping apparatus) used to makepolymeric resin items.

In the above-mentioned specific implementation of the present inventionfor use with the fabrication of polymeric resin molds for plasticorthodontic appliances, a dentist makes a cast or an impression of apatient's upper and/or lower dental arches, and then sends the casts orimpressions to an orthodontic appliance manufacturing facility. Themanufacturing facility scans the casts or impressions (e.g., by CTscanning), and creates an electronic data or treatment file thatincludes the treatment information for the patient. The treatmentinformation typically includes the scanned and digitized image of thecast or impression, the number of incremental positioning steps or“stages” for both the upper and lower dental arches that are requiredfor each patient to reposition the patient's teeth, the position of theteeth in each stage, and how the teeth are moved between each successivestage.

The SLA builds a batch of items (such as molds) from polymeric resin,layer-by-layer, on a tray or platform. The tray or platform leaves or isremoved from the SLA with the resin items on it in an uncured state, inwhich some of the resin may be in a liquid or semi-liquid state. In oneembodiment, the item itself is substantially cured and some of the resinin a liquid or semi-liquid state is disposed on the item. Excess resin,in a liquid or semi-liquid state, may also be left on the tray orplatform. At this point, the “post-processing” of the items may becommenced, in accordance with the present invention.

FIG. 1 is a block diagram of a system 100 for automating thepost-processing of items, particularly polymeric resin dental alignermolds, according to one aspect of the present invention.

As mentioned above, the molds are built on a tray in the SLA. Once themolds have been completely built, the trays on which the molds are builtare placed onto a conveyor belt or line (not shown) which transports thetrays through different processing stations in the automated system 100for performing multiple processes. Once the trays have completed allprocesses, the trays exit the system 100 onto an outgoing conveyor (notshown). One or more controllers (not shown), such as a programmablelogic controller (PLC), controls the operation of the system 100.

The conveyor line first transports the trays to a spin station 102. Thespin station 102 first detects that the trays have been loaded and locksthe trays into place on a turntable. Once locked into place, the traysare subject to periods of rotation in both the clockwise and counterclockwise directions at speeds up to 500 RPM. The rotation forces anyliquid or semi-liquid resin to flow off the molds and the trays bycentrifugal force. The liquid or semi-liquid resin is then filtered andcollected in a container for re-use. The spin station will be describedlater in detail, with reference to FIGS. 2, 3A, 3B, and 3C.

Upon completing the spin cycle, the trays are transported on theconveyor line to a washing apparatus 104 (described in detail below),which, in a preferred embodiment of the invention, is a closed-loop,high pressure, high temperature water spraying system. The high pressurewater spray removes excess material, such as resin, from the items 505.Once the wash cycle is completed, the trays are transported to a highpowered UV curing station 106 to cure the resin of the items 505. In theUV curing station 106, UV lamps (not shown) are advantageouslyreciprocated back and forth, exposing the items 505 to short doses ofhigh-intensity UV radiation, instead of a single, long-term dose as isconventionally done.

From the UV curing station 106, the trays are transported to a mold andsupport removal station 107. The items 505 such as molds are attached tothe tray with a sacrificial layer of the cured polymer. The removalstation 107 applies sufficient pressure to the items 505 to break thesacrificial layer and separates the items 505 from the trays, withoutdamaging the items 505. The removal station can further include agrinding plate to grind the items 505 to remove any excess sacrificiallayer of the cured polymer and ensure a flat bottom, and presents theitems 505 for example, molds for the next process in creating aligners.

From the mold and support removal station 107, the trays 504 (withoutthe items) are transported to a tray cleaning station 108 where the tray504 is cleaned by spraying water at high pressure to remove anypolymeric resin material that is present on the tray. Cleaned trays areinspected and reused for the creation of the items, like the polymericresin mold items.

FIG. 2 shows an exemplary spin station 102. The spin station 102includes a loading mechanism 501 that receives a tray 504 on whichpolymeric resin items 505, such as aligner molds, have been formed bymeans such as an SLA. The spin station further includes a spin chamber507 to rotate the tray 504, and an unloading mechanism 502 to presentthe tray 504 after the tray 504 has been subject to rotation in the spinchamber 507. The spin chamber 507 includes a shroud 503, a turntable(not shown) and a collection bin 506. In one embodiment, the loadingmechanism 501 may be configured to receive a plurality of trays 504 in astacked arrangement, a lift mechanism to raise the trays 504 one at atime to a chamber loading position, and a load arm (not shown) operableto move the tray 504 from the loading position to a turntable in thespin chamber 507 as described below. The unloading mechanism 502 isoperable to remove the tray 504 from the spin chamber 507 after the tray504 has been subject to rotation.

The shroud 503 includes a top and a bottom portion and is configured tobe movable from a closed position to an open position. In FIG. 2, theshroud 503 is shown in its closed position, surrounding the turntableconfigured to receive the tray and rotate the tray, details of whichwill be described in greater detail below, when further describingvarious aspects of the spin chamber 507. When the shroud 503 is in itsclosed position, the lower part of the bottom portion of the shroud 503is inside the collection bin 506. When the shroud 503 is in its openposition, access is permitted to the turntable for removable attachmentof the tray to the turntable. In one embodiment, the inner wall of theshroud 503 is coated with a material conducive to permit the liquidpolymer component that may be released from the items 505 and land onthe inner wall of the shroud 503 to flow toward the bottom portion ofthe shroud 503 and drip into the collection bin 506 when the tray 504 isrotated. In another embodiment other parts of the spin chamber 507 maybe coated with a material conducive to permit the liquid polymercomponent that may be released from the items 505 to slide down and dripinto the collection bin 506. For example, the inner wall of the shroudand other parts of the spin chamber 507 may be coated with a PTFEcompound such as TEFLON®, a material available from DuPont. In anotherembodiment, the side wall of the shroud 503 may be inclined inward fromthe top portion to the bottom portion so as to assist in the flow of theliquid toward the bottom portion of the shroud. In yet anotherembodiment, part of the bottom portion of the shroud may include aninwardly-tapered surface, which may further assist the flow of theliquid and permit the collection of the liquid in the collection bin506. In one embodiment, the collection bin 506 may include a base and aside wall, with the side wall surrounding a portion of the bottomportion of the shroud 503 when the shroud 503 is in a closed position.The collection bin 506 may further include an outlet (not shown) todrain the liquid collected in the collection bin. The outlet (not shown)may be located in the side wall or the base of the collection bin 506.The base of the collection bin 506 may further be configured to besloped toward the outlet (not shown), to permit the flow of the liquidtoward the outlet of the collection bin 506. The collection bin 506 mayfurther include an opening (not shown) to permit a turntable 509(described below) to pass through the collection bin and rotate the tray504.

FIG. 3A shows an exemplary spin chamber 507 mounted on a platform 508 towhich the collection bin 506 is attached. The platform 508 may alsoinclude frames and pillars to hold various transmitter/receiver pairsand provide rigidity to the spin chamber 507. The spin chamber 507includes a turntable 509 that is operable to rotate about an axis A-A. Ashroud plate 520 is coupled to an actuator (not shown) and moves alongthe axis A-A, when the actuator is actuated. The shroud 503 (not shown)is attached to the shroud plate 520 to move the shroud 503 from a closedposition to an open position, by activating the actuator. In oneembodiment, the turntable 509 is attached to a pulley (not shown) thatis driven by a belt coupled to an electric motor (not shown). Theturntable 509 is configured to receive the tray 504 from the loadingmechanism 501 at a load side 516 of the spin chamber 507 and hold thetray 504 when the turntable 509 is rotated. The turntable 509 is furtherconfigured to permit the tray 504 to be moved to the unloading mechanism502 at an unload side 518 of the spin chamber 507. The turntable 509 mayinclude one or more position sensors (not shown) to determine the radialposition of the turntable 509 in relation to a reference point. Theposition sensor(s) may be used to orient and position the turntable 509,for example, to receive the tray 504 from the loading station 501 at theload side 516 of the spin chamber 507. Similarly, the position sensor(s)may be used to orient and position the turntable 509 so as to permit theremoval of the tray 504 to the unloading mechanism 502 at the unloadside 518 of the spin station 507. The position sensor(s) may an includeconventional optical and/or magnetic encoder assembly capable of sensingangular movement of the turntable 509, and the sensor(s) may be includedin the motor driving the turntable 509.

In one embodiment, the turntable 509 is configured to removably hold thetray 504 in a position such that increased centrifugal force is appliedto the item 505 when the turntable 509 is rotated. In an embodiment, thetray 504 is held radially offset from the axis of rotation A-A of theturntable 509. In an embodiment, the tray 504 is held in a verticalposition radially offset from the axis of rotation A-A of the turntable509, although tray 504 may be held in other orientations. The turntable509 includes a pair of stationary clamps 510 and a movable clampassembly 511 to removably hold the tray 504. The stationary clamps 510hold the tray 504 near one of the edges of the tray 504 and the movableclamp assembly 511 holds the tray 504 near the edge opposite to theedges of the tray 504 held by the stationary clamps 510. The movableclamp assembly 511 is movable between an open position and a closedposition. The detailed structure and operation of the movable clampassembly 511 will be described below, with reference to FIG. 3B and FIG.3C.

The spin chamber 507 may include several sensors to confirm the presenceof the tray 504, the proper orientation of the tray 504, and thelocation of the turntable 509. In one embodiment, the spin chamber 507on the load side 516 may include a sensor to confirm that the turntable509 is properly aligned on the load side 516, to receive a tray 504 fromthe loading mechanism 501. This may, for example, be implemented byusing one or more optical transmitter-receiver pairs 522,524 of a typewell-known in the art. The optical transmitter and optical receiver pairare mounted on the platform 508 at positions corresponding to the properalignment of the turntable 509 to receive a tray 504 from the loadingstation 501. The stationary clamp 510 on the turntable may include athrough-hole that would permit the light beam transmitted from theoptical transmitter to pass through the through-hole and reach theoptical receiver only when the turntable 509 is properly oriented toreceive the tray 504 from the loading mechanism 501. Similar opticaltransmitter-receiver sensor pairs 530, 532 can be mounted in the unloadside 518 of the spin chamber 507 to indicate when the turntable 509 isproperly aligned with the unloading mechanism 502, to unload the tray504. Similar optical transmitter-receiver sensor pairs can be mounted onthe platform 508 to confirm the presence of the tray 504 and to confirmthat the tray 504 is not tilted.

Various parts of the turntable 509 are assembled using fasteners. In oneembodiment, the fasteners are wire locked to ensure that various partsof the turntable 509 are held together and withstand the centrifugalforce imparted on the turntable 509 during the operation of the spinstation.

FIG. 3B shows the movable clamp assembly 511 in the closed position.FIG. 3C shows the movable clamp assembly 511 in the open position. Themovable clamp assembly 511 includes a clamp arm 512 that is pivotallymounted on the turntable 509 so as to swing between an open position anda closed position. The clamp arm 512 further includes a clamp 513 at adistal end, configured to hold the tray 504 near the edges of the tray504 when the clamp arm 512 is in closed position. The clamp arm 512 isbiased by a spring 515 so that the clamp arm 512 is normally in theclosed position. The clamp arm 512 further includes a head 514 at adistal end away from the clamp 513 so that a plunger 516 actuated by anactuator 517 may engage with the head 514 and swing the clamp arm 512about the pivot to move the clamp arm 512 from the closed position tothe open position.

The turntable 509 of the spin chamber 507 may be configured to receiveone or more trays 504. When the turntable 509 is loaded, for example,with two trays, it may be advantageously loaded on both sides of theturntable 509, to assist in the balancing of the load on the turntable509. The operating parameters of the turntable 509 may be differentdepending upon the number and characteristics of the tray 504 theturntable 509 is rotating. The turntable 509 is operable to rotate inboth clockwise (CW) and counter-clockwise (CCW) directions, and it isfurther operable to accelerate to the desired rotational speed, and todecelerate therefrom to a stop at different rates (“ramp-up time” and“ramp-down time”, respectively). It may also be operable to pause for aspecified “dwell time” before restarting the rotation. The tray 504 maythus be subject to rotation both in the clockwise and counter-clockwisedirections, for different spin times, rotational speeds, ramp-up times,ramp-down times, and dwell times, to achieve efficient removal of excessmaterial. In the preferred embodiment of the present invention,exemplary process parameters and limits for the turntable 509 areidentified below, for a turntable rotating a single tray 504 and twotrays 504. It should be noted that any suitable process parameters andlimits may be used.

Ramp up Rampdown Single Spin time 0 to time max Tray Rotational Time maxRPM RPM to 0 Dwell Cycle Direction RPM (seconds) (seconds) (seconds)(seconds) Spin1 CW 300 30 5 5 2 Spin2 CCW 300 30 5 5 2 Spin3 CW 300 30 55 2 Spin4 CCW 300 30 5 5 2

Ramp up Ramp down Two Spin time 0 to time max Tray Rotational Time maxRPM RPM to 0 Dwell Cycle Direction RPM (seconds) (seconds) (seconds)(seconds) Spin1 CW 400 30 5 5 2 Spin2 CCW 400 30 5 5 2 Spin3 CW 400 30 55 2 Spin4 CCW 400 30 5 5 2

FIG. 4 is a block diagram of an exemplary washing apparatus 104 for usein the system of FIG. 1. The conveyor line or belt transports the traysto a plurality of processing stations (described below) to perform asequence of post-processing functions in a continuous fashion. Forexample, the conveyor line or belt may transport a tray 504 that hasbeen processed through the spin chamber 507 and unloaded to theunloading mechanism 502. In the alternative, tray 504 may be manuallyloaded into the unloading mechanism 502. A sensor (not shown) may sensethe presence of a tray 504 in the unloading mechanism 502 and transportthe tray 504 to a plurality of processing stations (described below).The stations advantageously include the following: a loading station110, a washing station 112, an isolation station 114, a rinsing station116, a drying station 118 and an unloading station 120. The trays aretransported from the spin station 102 first to the loading station 110.Once the trays are loaded, the conveyor line transports the trays to thewashing station 112. As described in detail below, in the washingstation 112 hot water is sprayed on the items as they pass through,thereby removing most of the excess resin from the items.

The conveyor line then transports the trays from the washing station 112to the isolation station 114, where high pressure air blows anyremaining water off of the molds. From the isolation station 114, thetrays 504 are transported to the rinsing station 116, where anyremaining residue, debris, or excess material is removed from the itemsby another hot water spray, as described below. As will be seen below,the rinsing station 116 may advantageously be substantially identical tothe washing station 112, with the exception that the water sprayed ontothe items is cleaner.

In the rinsing station 116, the trays and items accumulate water. Toremove the accumulated water, the trays 504 are transported to thedrying station 118. The drying station 118, as with the isolationstation 114, uses high pressure air to blow off the excess water. Oncethe excess water is blown off, the trays 504 are transported to theunloading station 120 where the trays 504 are transferred to adownstream conveyor.

FIGS. 5A and 5B illustrate a flow schematic of a water filtering system111, according to one aspect of the present invention. First, the trays504 are transported on the conveyor line to the washing station 112 forremoving excess resin. The washing station 112 has three top spray bars122-126 and three bottom spray bars 128-132 for spraying watersimultaneously onto the tops and bottoms, respectively, on the items 505to wash off excess polymeric resin material from the items 505 on thetrays 504. The washing station 112 may include an air handling system290 operable to remove air mixed with water particles (which may furthercontain traces of polymeric resin materials) that may be formed in thewashing station 112 when the water is sprayed under pressure on to theitems 505. The air handling system 290 will be described in detailbelow. The water is maintained at an elevated temperature, e.g., in therange of about 110° F. (43° C.) to about 140° F. (60° C.), to enhancethe removal of the excess material from the items 505. The temperatureof the water is preferably maintained at such a level that thetemperature of the item 505 is substantially maintained as close to butbelow the temperature at which the item 505 may deform to an extentwhere the item 505 may not be functionally useful. In one embodiment,the temperature of the water is preferably maintained at such a levelthat the temperature of the item 505 is substantially maintained asclose to but below the heat deflection temperature of the material theitem 505 is made of. In a preferred embodiment of the present invention,the temperature of the water used in the washing station 112 ismaintained at about 130° F. (55° C.) and the pressure of the water ismaintained at about 30 psi.

Now referring to FIG. 8, the air handling system 290 includes a ductwith an inlet 294 and an outlet 296, and a blower 298. The blower 298 isconnected to the outlet 296 of the air handling system 290 to draw theair mixed with water particles (which may contain traces of polymericresin material) from the inlet 294, toward the outlet 296. In oneembodiment, a mist removal station 300 may be connected to the duct 292,between the inlet 294 and the outlet 296 to separate water particles(which may further contain traces of polymeric resin material) containedin the air mixed with water particles. The air handling system 290 whenoperational, maintains a negative air pressure in the vicinity of theinlet 294 to assist in the removal of the air mixed with water particlesformed in the washing station 112, toward the outlet 296. The mistremoval station 300 may include one or more separation stations 302 toseparate the water particles from the air water mixture. One or moreseparation stations 302 may be connected in series to pass the air mixedwith water particles through successive separation stations. In one ofthe separation station 302, air mixed with water particles are passedover plates 304 that are curved. For example, the plates may be chevronshaped. The plates may be made of stainless steel. The plates may beseparated by a gap of about one inch to three inches, preferably aboutone and a half inches to permit the flow of air mixed with water. Whenthe air mixed with water particles flows over the curved plates, waterparticles settle on the surface of the plates. Water particles collectedon the plates flow toward the edges of the plates and are collected inthe collection chute 320 and fed to the water filtering system 111,which will be described in detail later. In one embodiment, the mistremoval station 300 may include another separation station 302 with oneor more mesh 306 with fine pores through which the air mixed with waterparticles pass through. In one embodiment, the fine pores in the mesh306 may be of the order of 200 microns. In one embodiment, the mesh 306may be made of stainless steel. In one embodiment, multiple meshes 306may be packed together to form a thick pack of mesh 306. The thicknessof the pack of mesh 306 may be in the range of about two inches to about12 inches, preferably, about six inches. Any water particles trapped inthe mesh 306 will flow down and are collected in the collection chute302 and fed to the first holding tank 200 of the water filtering system111, which will be described in detail later. From the washing station112, the trays are transported on the conveyor line to the isolationstation 114 (see FIG. 4). The isolation station 114 uses high pressureair to blow off the water from the items 505. From the isolation station114, the trays 504 are transported to the rinsing station 116. Therinsing station 116, as with the washing station 114, has three toprinse spray bars 134-138 and three bottom rinse spray bars 140-144 forspraying water onto the items to remove excess resin not removed in thewashing station 112.

Now referring back to FIG. 7, the rinsing station 116 may furtherinclude a second air handling system similar to the air handling system290 as previously discussed. For example, the inlet 310 of a second duct308 may be connected to the rinsing station 116 and the outlet of thesecond duct 312 may be connected to a second blower (not shown) to drawair mixed with water particles (which may further contain traces ofpolymeric resin material) in the rinsing station 116 from the inlet 310of the second duct 308 toward the outlet of the second duct. In thealternative, the inlet 310 of the second duct 308 may be connected tothe rinsing station 116 and the outlet 312 of the second duct connectedto the duct of the air handling system 290 between the inlet 294 and theoutlet 296 of the duct 292 of the air handling system 290, so that theblower 298 of the air handling system 290 can be used to draw air mixedwith water particles from the rinsing station 116 through the inlet 310of the second duct 308 toward the outlet 296 of the duct 292 of the airhandling system 290. The air handling system 290 when operational,maintains a negative air pressure in the vicinity of the inlet 310 ofthe second duct 308 to assist in the removal of the air mixed with waterparticles formed in the rinsing station 116, toward the outlet 296 ofthe duct 292.

Similarly, a third duct 314 may be connected to the drying station 118to draw air mixed with water particles (which may further contain tracesof polymeric resin material) from the drying station 116. The inlet 316of the third duct 314 may be connected to the drying station 118 and theoutlet 318 of the third duct 314 connected to the duct 292 of the airhandling system 290 between the inlet 294 and the outlet 296 of the duct292 so that the blower 298 of the air handling system 290 can be used todraw air mixed with water particles from the drying station 118 throughthe inlet 316 of the third duct 314 toward the outlet 296 of the duct292 of the air handling system 290. The air handling system 290 whenoperational, maintains a negative air pressure in the vicinity of theinlet 316 of the third duct 314 to assist in the removal of the airmixed with water particles from the drying station 118, toward theoutlet 296 of the duct 292. As one skilled in the art would appreciate,the diameter of the ducts 292, 308 and 314 and inlets 294, 310 and 316are suitably selected to permit efficient removal of proper quantity ofair mixed with water particles (which may further contain traces ofpolymeric resin material). For example, in one embodiment, the diameterof the inlet 316 in the drying station 118 may be advantageously bebigger than the diameter of the inlets 294 and 310.

In the preferred embodiment, the water used in the rinsing station 116is cleaner than the water used in the washing station 112, as thecleaner water removes the final amount of residue on the molds. Thewater is maintained at an elevated temperature to enhance the removal ofthe excess material from the item. The temperature of the water ispreferably maintained at such a level that the temperature of the item504 is maintained as close to but slightly below the heat deflectiontemperature of the material from which the molds are made. In apreferred embodiment of the present invention, the temperature of thewater used in the rinsing station 116 is maintained at about 130° F.(55° C.), and the pressure of the water is maintained at about 30 psi. Awash tank 146 supplies water to the top and bottom spray bars 122-132 inthe washing station 112 and collects the contaminated water (i.e. thewater mixed with resin) for later filtration. The wash tank 146 isheated, preferably by an internal heater (not shown), or alternativelyby an external heat source (not shown), to maintain the desired elevatedwater temperature. A first wash tank level sensor 148 and a second washtank level sensor 150 monitor the water level in the wash tank 146 toensure that there is sufficient water for the washing station 112. Awater tank pump 152 is used to pump the water from the wash tank 146 tothe top and bottom wash spray bars 122-132. The water from the wash tank146 is split into a top spray bar line 154, for supplying water to thetop wash spray bars 122-126, and a bottom spray bar line 156 forsupplying water to bottom wash spray bars 128-132. A water tank pressuregauge 153 measures and visually displays the pressure of the waterexiting the water tank pump 152 for an operator to view.

A first wash pressure sensor 163 measures the pressure in the top spraybar line 154, and a second wash pressure sensor 165 measures thepressure in the bottom spray bar line 156. A first pressure gauge 162visually displays the pressure in the top spray bar line 154 and asecond pressure gauge 164 visually displays the pressure in the bottomspray bar line 156. The pressure sensors 163, 165 transmit, eithercontinuously or at frequent intervals, the measured values to the PLC.If a value is at an inappropriate level, the PLC can take theappropriate steps to correct the problem.

A thermocouple 166, operatively associated with the wash tank 146,measures the temperature of the water therein. A thermocouple with dualsensing elements may be used for increasing the accuracy of the watertemperature measurement. A substantially constant volume of water mustbe maintained in the wash tank 146 at a substantially constanttemperature. Accordingly, the thermocouple 166 and the first and secondwash tank level sensors 148, 150 send their measured values to the PLC,either continuously or at frequent intervals. If the measured values arenot within the desired ranges, the PLC can take the appropriate steps torestore the proper water level in the wash tank 146 and/or to adjust thewater temperature by controlling the water tank heater. Additionally,the water in the wash tank 146 may be recirculated using a wash tankrecirculation pipe 155 and a wash tank recirculation pump 157. The waterin the wash tank 146 may be recirculated using the recirculation pump157 to minimize water temperature gradient within the wash tank 146.

A rinse tank 168 supplies water to the top and bottom rinse spray bars134-144 in the rinsing station 116 and collects the contaminated waterfor later filtration. The rinse tank 168 is heated by means similar tothat described above for the wash tank 146, to maintain the watertherein at a suitable elevated temperature. A transfer pump 149 may beemployed to pump water from the wash tank 146 to the rinse tank 168, orvice versa. A first rinse tank level sensor 170 and a second rinse tanklevel sensor 172 monitor the water level in the rinse tank 168 to ensurethat there is sufficient water for the rinsing station 116. A rinse tankpump 174 is used to pump water from the rinse tank 168 into a top rinsespray bar line 176, for supplying water to the top spray bars 134-138,and a bottom rinse spray bar line 178 for supplying water to bottomspray bars 140-144. A rinse tank pressure gauge 173 measures andvisually displays the pressure of the water and also transmits a signalto the PLC to take corrective action if the water pressure is too highor too low.

A first rinse pressure sensor 188 measures the pressure in the top rinsespray bar line 176 and a second rinse pressure sensor 190 measures thepressure in the bottom rinse spray bar line 178. A first rinse pressuregauge 184 visually displays the pressure in the top rinse spray bar line176 and a second rinse pressure gauge 186 visually displays the pressurein the bottom rinse spray bar line 178. The sensors 188, 190 transmitthe measured values, either continuously or at frequent intervals, tothe PLC. If a value is not within the desired range, the PLC can takethe appropriate steps to correct the problem.

A rinse tank thermocouple 192, operatively associated with the rinsetank 168, measures the temperature of the water. A thermocouple withdual sensing elements may be used for increasing the accuracy of thetemperature measurement. A substantially constant level of water must bemaintained in the rinse tank 168 at a substantially constanttemperature. Accordingly, the thermocouple 192 and the first and secondrinse tank level sensors 170, 172 send their values to the PLC, eithercontinuously or at frequent intervals. If the measured values are notwithin the desired ranges, the PLC can take the appropriate steps torestore the proper water level and/or to adjust its temperature bycontrolling the rinse tank heater. Additionally, the water in the rinsetank 168 may be recirculated using a rinse tank recirculation pipe 175and a rinse tank recirculation pump 177. The water in the rinse tank 168may be recirculated using the rinse tank recirculation pump 177 tominimize water temperature gradient within the rinse tank 168.

For example, when there are no items 505 to be processed through thesystem, it may be advantageous to stop the operation of various pumpsand circulation of water through the system, however, the water in thewash tank 146 and the rinse tank 168 may be advantageously berecirculated using the recirculation pump 157 and 177 while keeping theheater on in the wash tank 146 and the rinse tank 168. The recirculationof the water in the wash tank 146 and the rinse tank 168 mayadvantageously minimize the water temperature gradient in the wash tank146 and the rinse tank 168 so that the water is accurately maintained atthe elevated temperature and there is minimal startup time to initiatethe cleaning operation once the items 505 are available for cleaning inthe washing station 112 and the rinsing station 116.

To purify the contaminated water (including the resin) collected in thewash tank 146 and the rinse tank 168, the water from the tanks isremoved by manually opening a wash tank valve 194 and a rinse tank valve196. During normal operation of the washing station 112 and the rinsingstation 116, the manual water tank valve 194 and the rinse tank valve196 are in their open position. A holding tank pump 198 then pumps thewater into a first holding tank 200 (FIG. 5B) having a sloped bottom forcollecting the resin. In addition, a portion of the resin rises to thetop of the wash tank 146 and the rinse tank 168 and forms a resin foam.The wash tank 146 and the rinse tank 168 are configured such that theresin foam along with water is removed from the wash tank 146 and therinse tank 168 and collected in the first holding tank 200.Specifically, in one embodiment, the wash tank 146 and the rinse tank168 are provided with overflow pipes 159, 179 connected to the firstholding tank 200. By maintaining an excess flow of water into the washtank 146 and the rinse tank 168, the excess water flowing into the washtank 146 and the rinse tank 168 can advantageously remove the resin foamfrom the wash tank 146 and the rinse tank 168 through the overflow pipes159, 179 to the first holding tank 200. The first holding tank 200 isadvantageously provided with at least one water level sensor (not shown)for monitoring the water level therein and generating a water levelsignal that may advantageously be used to control the flow of water andthe operation of the system. A portion of the resin that has beenremoved from the items and mixed with the water settles on the bottom ofthe holding tank 200, as resin is denser than water. The resin that hassettled on the sloped bottom of the first holding tank 200 isperiodically removed and may be re-used or disposed off properly. Inaddition, a portion of the resin that has been removed from the itemsand mixed with the water may not settle on the bottom of the holdingtank 200, as for example, the resin foam that floats on the top of thewash tank 146 and the rinse tank 168. The water mixed with the resinfoam is further processed in the distillation system 210, as describedin detail below.

Referring to FIG. 5B, from the first holding tank 200, contaminatedwater passes through a manual valve 206, and then flows through one oftwo different routes. In the first route, a distillation valve 208 isopened causing the water to flow into a distillation system 210 wherethe water is evaporated under a vacuum (as opposed to under atmosphericpressure). The benefit of evaporating under vacuum is that any liquid,including water, evaporates at a lower temperature than at ambient(atmospheric) pressure. Thus, in the distillation system 210 of thepresent invention, evaporation takes place at room temperature. Thewater flows to the distillation system 210 from the first holding tank200 due to vacuum maintained in the distillation system 210, and a pumpis not needed. The valves 206 and 208 are in open position during thenormal operation of the distillation system 210.

The evaporated water vapor from the distillation system 210 is condensedin a separate tank within the distillation system 210 (described belowwith reference to FIG. 6). For a period of time, the distillation system210 is constantly evaporating contaminated water and then retrievingpurified water from the vapor. The contaminants (e.g. resin) from thewater fall to the bottom of the tanks and are gradually removed.

The purified water from the distillation system 210 is collected in asecond holding tank 212. A first water level sensor 227 and a secondwater level sensor 229 indicate the water level inside the secondholding tank 212. Signals from these sensors may advantageously be usedto control the flow of water into and out of the second holding tank212. A thermocouple 234, operatively associated with the second holdingtank 212, measures the temperature of the water therein.

Upon opening a second holding tank outlet valve 225, a holding tank pump214 pumps the water out of the second holding tank 212, as needed, toreplenish water in the wash tank 146 and the rinse tank 168. If waterfrom the second holding tank 212 is transferred to the wash tank 146, afirst transfer valve 216 is opened, allowing the water to flow into thewash tank 146. If the water from the second holding tank 212 istransferred to the rinse tank 168, a second transfer valve 218 isopened, allowing the water to flow into the rinse tank 168. Duringnormal operation of the distillation system 210, the valves 216, 218 and225 are in their open position.

Referring again to FIG. 5A, water (preferably from a municipal orprivate water line 220) is processed through a water softener to removeminerals that may be harmful to the operation of the system and then fedinto the rinse tank 168 and the wash tank 146 when a pair of main valves226, 228 and a pair of tank-filling valves 230, 232 are opened. Thedefault position of the tank-filling valves 230, 232 is open. The waterthat is being used is at a high temperature, around 130° F. (55° C.),and thus there is a constant water loss in the form of water vapor. Tocompensate for the loss, the water from the line 220 may be used to fillthe tanks 146, 168.

In the second route from the first holding tank 200, a bypass valve 209is opened, causing the water to bypass the distillation system 210. Thisis typically done when maintenance on the system is required. Duringmaintenance, the water is drained from the system so that the system canbe cleaned. A drain pump 222 pumps water from the first holding tank 200to a third holding tank 224. A third holding tank water level sensor 223communicates with the PLC. If the water level in the third holding tank223 reaches tank capacity, the PLC automatically closes the bypass valve209, preventing the third holding tank 224 from overflowing.

FIG. 6 is a block diagram of the distillation system 210 of FIG. 5B. Thedistillation system 210 is a closed-loop filtration system that purifieswater from the system 100 for automating the post-processing of items.In the distillation system 210, the contaminated water is fed into afirst reaction chamber 250 and a second reaction chamber 252. The wateris evaporated using heat in the first reaction chamber 250 and thesecond reaction chamber 252, and then it is cooled in a first productchamber 254 and a second product chamber 256 through a standardrefrigeration process. Although the system is described with tworeaction chambers and two product chambers, a system can beadvantageously built using a single reaction chamber and a singleproduct chamber.

A compressor 251 is used to heat a refrigerant, and the heatedrefrigerant is fed into the first reaction chamber 250 and the secondreaction chamber 252 through a first reaction coil 253 and a secondreaction coil 255, respectively. The contaminated water in the firstreaction chamber 250 and the second reaction chamber 252 boils when itcomes in contact with the hot refrigerant-filled reaction coils 253,255, causing the contaminated water to evaporate at low temperatureunder vacuum (achieved with a vacuum pump, not shown). This processleaves a resin residue in the first reaction chamber 250 and the secondreaction chamber 252. The outer surfaces of the first reaction coil 253and the second reaction coil 255 are made of a material or coated with amaterial that can withstand the high temperature and that is notconducive to adhesion of the resin residue. In one embodiment, the firstreaction coil 253 and the second reaction coil 255 are made of stainlesssteel, to which the resin residue does not adhere.

The resulting vapor enters a first product chamber 254 and a secondproduct chamber 256, respectively. The refrigerant is then condensed byrunning it first through an air-cooled condenser 261 and then throughone or more expansion valves 262. This cooled refrigerant is thensupplied to the first product chamber 254 and the second product chamber256 through a first product coil 258 and a second product coil 260. Thefirst product coil 258 and second product coil 260 condense the vaporback into water, creating purified water that is pumped to the secondholding tank 212, using a product pump 268, for use in the wash tank 146and the rinse tank 168. Refrigerant exiting the first product chamber254 and the second product chamber 256 may be stored in a reservoir 264and then supplied to the compressor 251 to close the refrigeration loop.A first reaction chamber sensor 270 and a second reaction chamber sensor272 indicate water level inside the first reaction chamber 250. A firstproduct chamber sensor 274 and a second product chamber sensor 276indicate water level inside the first product chamber 254. Signals fromthese sensors may be advantageously used to control the flow of waterand the operation of the system. The second reaction chamber 252 and thesecond product chamber 256 may be advantageously constructed to havesame sensors as described for the first reaction chamber 250 and firstproduct chamber 254.

System Flow Control

FIG. 7 shows the closed loop water flow control logic for the exemplarywashing apparatus of FIGS. 5A and 5B. Various signals from the sensorsare used by PLCs to operate various components of the system. Forexample, the PLCs can be programmed to operate valves and pumps, basedupon a predetermined logic and sensor outputs.

Rinse Tank Flow and Control

If the water level in the rinse tank 168 is at or below a Rinse TankOperating Low (RTOL) level, and if the water level in the second holdingtank 212 is at or above a Second Holding Tank Operating Low (SHTOL)level, the second holding tank outlet valve 225 is opened, and theholding tank pump 214 is started to supply purified water from thesecond holding tank 212 to the rinse tank 168. If, on the other hand,the water level in the second holding tank 212 is below the SHTOL level,the main valves 226, 228 are opened, and city water is supplied to therinse tank 168. When the water level in the rinse tank 168 is at orabove a Rinse Tank Operating High (RTOH) level, the holding tank pump214 is stopped, the second holding tank outlet valve 225 and the mainvalves 226, 228 are closed. If the water level in the rinse tank 168reaches is at or below a Rinse Tank Low (RTL) level, the rinse tank pump174 and the heater in the rinse tank 168 are turned-off to avoidcavitation and over-heating of heater elements (not shown). In addition,a “Rinse Tank Low Level” message may be displayed on a visual displaydevice (not shown), and, optionally, an audible alarm (not shown) may beactuated. If the water level in the rinse tank 168 is at or above theRinse Tank High (RTH) level, the washing apparatus 104 is stopped. Inaddition, a “Rinse Tank High Level” message may be displayed, and anaudible alarm may be actuated. The first rinse tank level sensor 170 canbe configured to provide a signal to indicate the RTOL level and thesecond rinse tank level sensor 172 can be configured to provide a signalto indicate the RTOH level. The first water level sensor 227 of thesecond holding tank 212 can be configured to provide a signal toindicate the SHTOL level of the second holding tank 212. Similarly,additional sensors in the rinse tank 168 can be configured to providesignals to indicate the RTL level and RTH level.

Wash Tank Flow and Controls

If the water level in the wash tank 146 is at or below a Wash TankOperating Low (WTOL) level, and if the water level in the rinse tank 168is at or above RTOL level, the transfer pump 149 is started to transferwater from the rinse tank 168 to the wash tank 146. If the water levelin the wash tank 146 is at or above a Wash Tank Operating High (WTOH)level, the transfer pump 149 is stopped. If the water level in the rinsetank 168 is below the RTOL, water is not transferred from the rinse tank168 to the wash tank 146. If the water level in the wash tank 146 is ator below a Wash Tank Low (WTL) level, the water tank pump 152 and aheater (not shown) in the wash tank 146 are turned-off to avoidcavitation and over-heating of heater elements (not shown). In addition,a “Wash Tank Low Level” message may be displayed, and an audible alarmmay be actuated. If the water level in the wash tank 146 is at or abovea Wash Tank High (WTH) level, the washing apparatus 104 is stopped. Inaddition, a “Wash Tank High Level” message may be displayed, and anaudible alarm may be actuated. The first wash tank level sensor 148 canbe configured to provide a signal to indicate the WTOL level, and thesecond wash tank level sensor 150 can be configured to provide a signalto indicate the WTOH level signal. Similarly, additional sensors in thewash tank 146 can be configured to provide signals to indicate the WTLlevel and WTH level.

First Holding Tank

If the water level in the first holding tank 200 is at or below a FirstHolding Tank Operating Low (FHTOL) level, and if the water level in thewash tank 146 is above the WTOL level, the holding tank pump 198 isstarted to fill the first holding tank 200. If the water level in thewash tank 146 is below the WTOL level, no action is taken to fill thewater into the first holding tank. If the water level in the firstholding tank 200 is at or above a first holding tank Operating High(FHTOH) level, the holding tank pump 198 is stopped. If the water levelin the first holding tank 200 is at or above a first holding tank high(FHTH) level, a “First Holding Tank High Level” message may bedisplayed, and an audible alarm may be actuated. If the water level inthe first holding tank 200 is at or below a first holding tank Low(FHTL) level, the distillation system 210 is shut-down, and a “FirstHolding Tank Low Level” message may be displayed, and an audible alarmmay be actuated. The first holding tank level sensor 202 can beconfigured to provide a signal to indicate the FHTOL level, and thesecond holding tank level sensor 204 can be configured to provide asignal to indicate the FHTOH level signal. Similarly, additional sensorsin the first holding tank 200 can be configured to provide signals toindicate the FHTL level and FHTH level.

Distillation System

The distillation system 210 includes the first reaction chamber 250, thesecond reaction chamber 252, the first product chamber 254, and thesecond product chamber 256. The operation is described below withrespect to the first reaction chamber 250 and the first product chamber254. The second reaction chamber 252 and second product chamber 256 maybe configured to operate in a manner similar to the operation of thefirst reaction chamber 250 and the first product chamber 254.

If the water level in the first reaction chamber 250 is at or below afirst reaction chamber Operating Low (FRCOL) level, first reactionchamber solenoid valve 280 is opened, and water from the first holdingtank 200 is pulled into the first reaction chamber 250 under vacuum,through the first holding tank connecting pipe 278. If the water levelin the first Reaction Chamber 250 is at or above a first reactionchamber Operating High (FRCOH) level, the solenoid valve 280 is closed,and water flow from the first holding tank 200 to the first reactionchamber 250 is stopped. If the water level in the first reaction chamber250 is at or above a first reaction chamber High (FRCH) level, vacuuminside the distillation system 210 is released, and the distillationsystem is powered-off. The first reaction chamber level sensor 270 canbe configured to provide a signal to indicate the FRCOL level, and thesecond reaction chamber level sensor 272 can be configured to provide asignal to indicate the FRCOH level signal. Similarly, additional sensorsin the first reaction chamber 250 can be configured to provide signal toindicate the FRCH level.

If the water level in the first product chamber 254 of distillationsystem is at or above a first product chamber Operating High (FPCOH)level, the product pump 268 is turned on, and water is pumped from thefirst product chamber 254 to the second holding tank 212 through thesecond holding tank connecting pipe 284. If the water level in the firstproduct chamber 256 is at or below a first product chamber Operating Low(FPCOL) level, the product pump 268 is turned off, and water flow fromthe first product chamber 256 to the second holding tank 212 is stopped.If the water level in the first product chamber 254 is at or above afirst product chamber High (FPCH) level, vacuum inside the distillationsystem is released, and the distillation system is powered-off. Thefirst product chamber level sensor 274 can be configured to provide asignal to indicate the FPCOL level, and the second product chambersensor 276 can be configured to provide a signal to indicate the FPCOHlevel signal. Similarly, additional sensors in the first product chamber254 can be configured to provide signal to indicate the FPCH level.

The second reaction chamber 252 and second product chamber 256 may beadvantageously constructed to have the same sensors and valves asdescribed above for the first reaction chamber 250 and the first productchamber 254.

Second Holding Tank:

If the water level in the second holding tank 212 is at or below asecond holding tank Low (SHTL) level, a “Second Holding Tank Low Level”alarm message may be displayed, and, an audible alarm may be actuated.If the water level in the second holding tank 212 is at or above asecond holding tank High (SHTH) level, the distillation system 210 isshut down, and a “Second Holding Tank High Level” alarm message may bedisplayed, and an audible alarm may be actuated. Additional sensors inthe second holding tank 212 can be configured to provide signals toindicate the SHTL level and the SHTH level.

In the preferred embodiment of the present invention, exemplary processparameters and limits are identified below. It should be noted that anysuitable process parameters and limits may be used.

Parameter Units Default Low Limit High Limit Conveyor Speed Fpm 1 0.51.5 Wash/Rinse Temperature F 130 110 140 Wash/Rinse Top Pressure Psi 3020 40 Wash/Rinse Bottom Pressure Psi 10 5 20 Air Flowrate Cfm 500 400600 Vacuum Level Torr 22 10 30 Low Pressure Psi 100 70 110 High PressurePsi 300 270 350 Reaction Chambers F 80 70 90 Temperature

Once the wash cycle is completed, the trays 504 are transported to ahigh powered UV curing station 106 to cure the resin of the items 505.In the UV curing station 106, UV lamps (not shown) are advantageouslyreciprocated back and forth, exposing the items 505 to short doses ofhigh-intensity UV radiation, instead of a single, long-term dose as isconventionally done. In one embodiment, the UV lamp intensity may be inthe range of about 1.5 watts/cm² to about 3 watts/cm² and preferably inthe range of 2.6 watts/cm². In another embodiment, the peak wavelengthof the UV lamp may be in the range of about 330 nanometers to about 390nanometers and preferably in the range of 360 nanometers. In oneembodiment, the items 505 are exposed to high intensity UV radiation,for about one to three minutes, and preferably for about two minutes.From the UV curing station 106, the trays 504 with the items 505 aretransported to a mold and support removal station 107.

The items 505 such as molds are attached to the tray 504 with asacrificial layer of the cured polymer. The removal station 107 appliessufficient pressure to the items 505 to break the sacrificial layer andseparates the items 505 from the trays, without damaging the items 505.The removal station can further include a mechanism to remove any excesssacrificial layer of the cured polymer and provide substantially flatbottom, and presents the items 505 for example, molds for the nextprocess in creating aligners.

The items 505 such as molds are attached to the tray 504 with asacrificial layer of the cured polymer. The tray 504 further includesmultiple thru holes 614, the thru holes 614 corresponding to thelocation of the items 505 on the tray 504. The diameter of the thruholes 614 may be in the range of about ⅛ inch to about ⅜ inch andpreferably about ¼ inch. The removal station 107 includes a detachmentstation 602, a transfer station 604 and a collection station 606. In thedetachment station 602, the item 505 is detached from the tray 504. Thetray 504 containing detached items 505 is moved to the transfer station604 by, for example, a conveyor belt. In the transfer station 604, theitems 505 are movably engaged for relative motion with respect to thetray 504 and the items 505 are moved from the transfer station 604 tothe collection station 606. In the collection station 606, any remainingsacrificial layer is removed from the items 505 and the items arecollected for further processing.

Now, referring to FIG. 9, the tray 504 is received and positioned in thedetachment station 602, for the detachment of the items 505 from thetray 504. The detachment station 602 includes a pin plate 608 with aplurality of pins 610. The pin plate 608 is attached to an actuator 612to move the pin plate 608. The pins 610 of the pin plate 608 are alignedto pass through the thru holes 614 of the tray 504 when the pin plate608 is moved. The diameter of the pins 610 of the pin plate 608 isselected to be slightly less than the diameter of the thru holes 614 inthe tray 504, to permit free movement of the pins 610 through the thruholes 614 of the tray 504. When the pin plate 608 is moved, the pins 610enter the thru holes 614 from the bottom of the tray 504, pass throughthe thru holes 614 of the tray 504 and then engage with the items 505 onthe tray 504. After engaging with the items 505, the pin plate 608 isfurther moved to apply sufficient pressure to the item 505 so as tobreak the sacrificial layer of the item 505 that is attached to the tray504. A pressure of about 2 to about 50 psi and preferably about 30 psiis applied to the items 505. The tray 504 is held stationary, when thepin plate 608 is moved. In one embodiment, the movement of the pin plate608 is limited by a stop (not shown) to prevent excessive penetration ofthe pins 610 through the tray 504 so as to prevent damage to the item505. In one embodiment, a cover plate 616 may be positioned on top ofthe tray 504 so as to confine the movement of the items 505 after theitems 505 are detached from the tray 504. In one embodiment, the coverplate 616 may include one or more projections 618 to engage with tray504 and hold the tray 504 stationary, when the pin plate 608 is moved todetach the item 504 from the tray 505. In one embodiment, the coverplate 616 may be attached to an actuator 620 to move the cover plate 616to position the cover plate 616 on top of the tray 504, and furtherengage with the tray 504 and hold the tray 504 stationary, when the pinplate 608 is moved to detach the item 504 from the tray 505. In oneembodiment, the underside of the cover plate 616 facing the items 505may include a layer of compliant material 622, to minimize any damage tothe item, if the item 504 strikes the underside of the cover plate 616.For example, a layer of compliant foam like Poron available from DuPontmay be used. The thickness of the compliant material may be in the rangeof about 0.5 inches to 1.5 inches and preferably about one inch.

After the items 505 have been detached from the tray 504 in thedetachment station 602, the tray 503 with loose items 505 is moved tothe transfer station 604. The transfer station 604 includes a transferplate 624. The transfer station 604 further includes a transfermechanism. The transfer mechanism is configured to move the transferplate 624 in one or more directions. In one embodiment, the transfermechanism moves the transfer plate 624 toward the tray 504 and thetransfer plate 624 engages with the detached item 505 on the tray 504.The transfer plate 624 may include a plurality of pins 628 that aremovable. For example, the transfer plate 624 may include a bed ofmovable pins 628.

The transfer mechanism includes an actuator 650 and a stepper motor 658.The actuator 650 is operable to move an actuator arm 652. The actuatorarm 652 is attached to the transfer plate 624 and moves the transferplate 624 toward and away from the tray, when the actuator is actuatedand the actuator arm 652 is moved. The actuator 650 includes a bracket654 that rests on a rail 656 and the bracket 654 is configured to slidealong the rail 656. The stepper motor 658 includes a pulley 670 thatrotates when the stepper motor 658 is activated. A belt 670 couples thepulley 670 of the stepper motor 658 to the transfer plate 624 and movesthe transfer plate 624 when the stepper motor 658 rotates the pulley670. When the stepper motor 658 is actuated to move the transfer plate624, the transfer plate 624 moves along the direction of the rail 656,as the bracket 654 of the actuator 650 slides along the rail 656. Therail 656 is advantageously positioned to run from the transfer station604 to the collection station 606.

When the transfer plate 624 is moved toward the tray 504, by actuatingthe actuator 650, the movable pins 628 engage with the items 505 andsurround the item 505 by aligning themselves around the contour of theitem 505. In one embodiment, the transfer plate 624 is moved close tothe tray 504 so as to permit the movable pins 628 to surround the items505 on the top and the side, but not engage with the surface of the tray504 in locations where there is no item 504 present. In one embodiment,sufficient downward pressure is maintained on the movable pins 628 topositively maintain the engagement of the movable pins 628 with the item505 when the movable pins 628 are urged toward the item 505.

FIG. 9A shows the transfer plate 624. The transfer plate 624 includes abottom plate 630, a middle plate 632 and a top plate 634, all spacedapart and held together by a plurality of posts 636. The bottom plate630 and the middle plate 632 have thru holes that are dimensioned andaligned to permit free movement of the movable pins 628, between a fullyextended position and a fully retracted position. The movable pins 628have heads 538 that are bigger than the thru holes in the middle plate632 and the middle plate 632 acts as a stop and confines the movement ofthe movable pin 628 to its fully extended position, when the movablepins 628 fully extend through the bottom plate 630. The top plate 634 ispositioned to limit the movement of the movable pin 628 and act as astop, when the movable pin 628 is in its fully retracted position. Inone embodiment, a portion of the movable pin 628 is at least partiallylocated in the thru hole of the bottom plate 630. The diameter of themovable pins 628 may be in the range of about ⅛ inch to about ⅜ inch andpreferably about ¼ inch. In one embodiment, sufficient pressure isapplied to the movable pins 628 toward the item, to positively maintainthe engagement of the movable pins 628 with the item 505.

In one embodiment, the bottom surface of the top plate 634 may furtherinclude a compliant member 640 that imparts downward pressure to themovable pins 628 toward the item 505, when the pins are urged into thecompliant member 640, as the movable pins engage with the item 504. Inanother embodiment, the transfer plate 624 may further include a sideplate (not shown) that connects the sides of the top plate 634 and themiddle plate 632, to form an enclosure. In one embodiment, the sideplate may connect the sides of the top plate 634 and the bottom plate630 to form an enclosure. The side plate may further include an inlet toreceive air under pressure. By injecting air under pressure into theenclosure, a downward pressure can be imparted to the movable pinstoward the item 505, to further assist in positive engagement of theitems by the movable pins. The air pressure is maintained at such alevel to impart sufficient downward pressure to the movable pins 628,while accounting for air leakage through the thru holes in the middleplate and/or bottom plate, if any.

After the transfer plate 624 engages with the item 505, the transfermechanism moves the transfer plate 624 to the collection station 606.The stepper motor 658 is activated to move the transfer plate 624 towardthe collection station 606. As the transfer plate 624 moves to thecollection station 606, the items 505 surrounded by the movable pins 628are moved to the collection station 606. The tray 504 without the itemwill be further processed in the tray cleaning station 108, which willbe described in detail later.

The Collection Station 606 includes a collection plate 642, a debriscollector 644 and a finish bin 648. The collection plate 642 includes aplurality of thru holes 646 that open into the debris collector 644.After the transfer plate 624 moves the item 505 over the collectionplate 642 of the collection station 606, the transfer mechanism impartsa reciprocating motion to the collection plate 642, by rotating thestepper motor 658 in both clockwise and counter clockwise direction. Thereciprocating motion moves the items 505 relative to the collectionplate 642 and breaks any sacrificial layer attached to the item 505. Thebroken sacrificial layer debris pass through the thru holes 646 of thecollection plate 642 and is collected in the debris collector 644 forproper disposal. Then the transfer mechanism moves the transfer plate624 toward the finish bin 648 by operating the stepper motor 658 andpushes the items 505 into the finish bin 648. After moving the items 505into the finish bin 648, the transfer mechanism moves the transfer plate624 to the transfer station 604 by suitably operating the stepper motor658 and positions the transfer plate 624 in the transfer station 604.The actuator arm 652 is suitably moved by the actuator 650 to positionthe transfer plate 624 to process the next tray 504 with detached items505.

The tray 504 without the items is moved to the tray cleaning station 108to remove any cured resin material that may still remain on the tray504. For example, a conveyor line or belt may transport a tray 504 thathas been processed through the removal station 107 to the tray cleaningstation 108.

From the mold and support removal station 107, the trays 504 (withoutthe items) are transported to a tray cleaning station 108 where the tray504 is cleaned by spraying water at high pressure and high temperatureand remove any polymeric resin material that is present on the tray 504.Cleaned trays 504 are inspected and reused for the creation of theitems, like the polymeric resin mold items.

Now referring to FIG. 10, the tray cleaning station 108 includes a waterspraying mechanism 680 operable to spray water at elevated temperatureand pressure on the tray 504. The water spraying mechanism 680 includesa plurality of nozzles 682 to spray water at a flow rate of about twogallons per minute per nozzle to about eight gallons per minute pernozzle, preferably about four gallons per minute per nozzle and at apressure of about 1000 psi to 3500 psi, preferably about 3000 psi. Watermay be maintained at an elevated temperature, for example, from about120 degree F. to about 150 degree F., preferably about 140 degree F.Water spraying nozzles 682 are positioned such that water is sprayed onboth the top and bottom surface of the tray 504. In one embodiment, aplurality of rows of water spraying nozzles 682 is positioned to spraywater on the top surface of the tray 504. Similarly a plurality of rowsof water spraying nozzles 682 is positioned to spray water on the bottomsurface of the tray 504. The nozzles 682 may be positioned parallel toeach other and/or staggered with respect to each other to provideadequate coverage of the tray 504. In one embodiment, the tray 504 maybe advantageously moved relative to the water spraying nozzles 682. Inone embodiment, a conveyor 683 may move the tray 504 relative to thewater spraying nozzles 682, as the water spraying nozzles 682 spraywater on the tray. In one embodiment, the conveyor 683 may be of chaintype that engages the tray 504 at its edges and moves the tray 504relative to the water spraying nozzles 682. In another embodiment, thewater spraying mechanism 682 may oscillate and spray water on variouslocations of the tray 504. In yet another embodiment, a combination ofthe movement of the tray 504 and the movement of the water sprayingnozzles 682 may be used.

The water spraying mechanism 680 may further include a motor driven pump684 with pistons to pressurize the water to the desired pressure beforefeeding the water to the water spraying nozzles 682. The water sprayingmechanism 680 may further include a receiving tank 688 to hold waterthat will be used to spray on the tray 504 and to collect water that hasbeen sprayed on the tray 504. The receiving tank 688 may further includea heater 690 to heat the water to the desired temperature. The waterspraying mechanism 680 may further include a filter 686 connectedbetween the receiving tank and the pump 684, to filter and remove anyresin material released from the tray 504 before the water is fed to thepump 684. The water spraying mechanism 680 may include one or moresensors to measure the temperature of the water and the level of waterin the receiving tank 688. The sensor outputs may advantageously be usedby one or more PLCs to control the water spraying mechanism 680 and thetray cleaning station 108.

The tray cleaning station 108 may further include a steam removalmechanism 692 to remove any water particles mixed with air formed whenwater at high pressure and high temperature is sprayed on the tray 504.The steam removal mechanism 692 includes a chute 693 attached to ablower 694. The blower 694 is coupled to a motor 696. The blower 694when operated removes any water particles mixed with air through thechute 693 and the water particles mixed with air is exhausted throughthe exhaust 700.

After the tray 504 is subjected to high pressure water cleaning, thetrays 504 are moved to a tray drying station, where hot air is blownover the trays to remove any residual water remaining on the tray. Thetray 504 may be transported through the tray drying station using aconveyor, as air jets flow air over the tray 504. The dried trays 504may be reused in the creation of items like SLA molds.

In the system for processing polymeric resin items, the movement of thetrays 504 containing the items 505 can be automated by using a suitableconventional conveyor system (not shown), of a type well-known in theart. For example, the conveyor system can be configured to move the tray504 from the unload side 518 of the spin station 507 to the washingstation. The conveyor can be configured to move the tray 504 through thevarious stations. Specifically, referring to FIG. 1, the conveyor systemcan be configured to move the trays 504 from the spinning station 102 tothe washing apparatus 104, from the washing apparatus 104 to the curingstation 106, from the curing station 106 to the removal station 107 andfrom the removal station 107 to the tray cleaning station 108. Withinthe washing apparatus 104, the conveyor system can be further configuredto move the trays 504 from the loading station 110 to the washingstation 112, from the washing station 112 to the isolation station 114,from the isolation station to the rinsing station 116, from the rinsingstation 116 to the drying station 118, and from the drying station 118to the unloading station 120. The length of the conveyor system and thespeed of the conveyor system can be selected to permit the movement andpresentation of the trays 504 to the process stations based upon thecycle time of the process station while minimizing the idle time of theprocess station waiting for the receipt of a tray 504 to process. If,for example, a subsequent process station has a longer cycle time thanthe preceding process station, the conveyor length can be extended toadd sufficient delay in presenting the tray 504 to the subsequentprocess station, or the speed of the conveyor station can be varied toensure no manual intervention is required, and that the tray 504 ispresented to the subsequent process station when the latter is ready toreceive the tray 504 for processing.

While the present invention is described above with respect to what iscurrently considered its preferred embodiments, it is to be understoodthat the invention is not limited to that described above. To thecontrary, the invention is intended to cover various modifications andequivalent arrangements within the spirit and scope of the appendedclaims.

What is claimed is:
 1. A system for removing extraneous liquid polymerfrom polymeric items having a curable liquid polymer component, thesystem including a spin station, wherein the spin station comprises: aspin chamber having a load side and an unload side; a tray loaderoperable to receive one or more trays carrying a plurality of polymericitems having extraneous liquid polymer thereon; a turntable having anaxis of rotation and located in the spin chamber so as to receive theone or more trays from the tray loader at the load side of the spinchamber and to discharge the one or more trays from the unload side ofthe spin chamber, the turntable being operable to spin the one or moretrays about the axis of rotation so as to remove at least a firstquantity of the extraneous liquid polymer from the polymeric items by atleast one of a centrifugal force and a gravitational force when the oneor more trays are removably held radially offset from the axis ofrotation of the turntable after the one or more trays are received fromthe tray loader; and a tray loader operable to receive the one or moretrays from the turntable at the unload side of the spin chamber.
 2. Thesystem of claim 1, further comprising: a first sensor mechanism operablyassociated with the turntable so as to determine when the turntable ispositioned relative to the load side of the spin chamber for receivingthe one or more trays from the tray loader; and a second sensormechanism operably associated with the turntable so as to determine whenthe turntable is positioned relative to the tray unloader for deliveringthe one or more trays to the tray unloader.
 3. The system of claim 1,wherein the tray loader and the tray unloader are external to the spinchamber.
 4. The system of claim 1, wherein the first sensor mechanism isconfigured to determine radial position of the turntable in relation toa reference point.
 5. The system of claim 1, wherein the turntable isconfigured to hold the one or more trays at an inclined positionrelative to the turntable.
 6. The system of claim 1, wherein theturntable is configured to hold the one or more trays in a verticalposition relative to the turntable.
 7. The system of claim 1, whereinthe turntable is configured to removably hold each of the one or moretrays at a position that is radially offset from the axis of rotation ofthe turntable.
 8. The system of claim 1, wherein the turntable isoperable to spin in both a clockwise direction and a counter-clockwisedirection.
 9. The system of claim 8, wherein the turntable is operableto spin in alternating clockwise and counter-clockwise directions. 10.The system of claim 1, wherein the load side and unload side are locatedon opposite sides of the spin chamber.
 11. The system of claim 10,wherein the turntable is configured to receive trays on opposite sidesof the turntable so as to achieve a balanced load on the turn table. 12.The system of claim 1, wherein the turntable is operable to spin the oneor more trays at accelerated rotational speeds, decelerated rotationalspeeds, and combinations thereof during a spin cycle.
 13. The system ofclaim 1, wherein the turntable is operable to pause its rotation for aspecific dwell time.
 14. The system of claim 13, wherein the turntableis operable to resume its rotation after the dwell time has expired. 15.The system of claim 1, wherein the turntable is operable to spin at arotational speed between 300-400 rpm.
 16. The system of claim 12,wherein the turntable is operable to rotate in different directions atdifferent rotational speeds with different accelerations anddecelerations.
 17. The system of claim 1, wherein the polymeric itemsare dental appliance molds, and the extraneous liquid polymer is aresin.
 18. The system of claim 1, wherein the spin chamber includes atleast one of shroud and a collection bin.
 19. The system of claim 1,further comprising a cover plate positionable over the one or more traysin a position that limits the movement of the polymeric items.
 20. Thesystem of claim 19, wherein the cover plate includes a layer ofcompliant material configured to engage the polymeric items.
 21. A spinstation, comprising: a spin chamber having a load side and an unloadside; a tray loader operable to receive one or more trays carrying aplurality of polymeric items having extraneous liquid polymer thereon; aturntable having an axis of rotation and located in the spin chamber soas to receive the one or more trays from the tray loader at the loadside of the spin chamber, and to discharge the one or more trays fromthe unload side of the spin chamber, the turntable being operable tospin the one or more trays about the axis of rotation so as to remove atleast a first quantity of the extraneous liquid polymer from thepolymeric items by at least one of a centrifugal force and agravitational force when the one or more trays are removably held at anangled position radially offset from the axis of rotation of theturntable after the one or more trays are received from the tray loader;a first sensor mechanism operably associated with the turntable so as todetermine when the turntable is positioned relative to the load side ofthe spin chamber for receiving the one or more trays from the trayloader; a tray unloader operable to receive the one or more trays fromthe turntable at the unload side of the spin chamber; and a secondsensor mechanism operably associated with the turntable so as todetermine when the turntable is positioned relative to the tray unloaderfor delivering the one or more trays to the tray unloader.
 22. The spinstation of claim 21, wherein the turntable is operable to spin indifferent directions at different rotational speeds with differentaccelerations and decelerations.
 23. The spin station of claim 21,wherein the turntable is operable to spin in both a clockwise directionand a counter-clockwise direction.
 24. The spin station of claim 23,wherein the turntable is operable to spin in alternating clockwise andcounter-clockwise directions.
 25. The spin station of claim 21, whereinthe spin chamber is configured so as to allow the trays to be loadedalternating between opposite sides of the spin chamber.
 26. The spinstation of claim 21, wherein the turntable is operable to spin at arotational speed between 300-400 rpm.
 27. The spin station of claim 21,wherein the turntable is configured to hold the one or more trays at aninclined position relative to the turntable.
 28. The spin station ofclaim 21, wherein the spin chamber includes at least one of a shroud anda collection bin.